With many items of complex modern electronic equipment, it is not readily possible to determine if all components of the equipment are functioning correctly and, if not, which component is the source of the problem. For this reason, it is commonplace to provide, for each major component, an indicator light that either lights to show that an intermittently activated component is "on-line", or functioning properly, or alternatively lights to show that a component is no longer functioning (for whatever reason).
Indicator lights of this kind can be found in addition in other less complex situations such as lights to show a room is occupied or lights to indicate that an item has passed a test. For the sake of simplicity, all status-indicating lights will be referred to hereinafter as "on-line" lights regardless of the function involved. The most significant applications of the present invention are, however, in the field of the monitoring of electronic equipment.
It is known to have a malfunction warning system built into the equipment but, since these run off the same power source, a catastrophic failure also shuts down the warning system. In addition, it is very difficult to retro-fit an existing system with such warning systems without violating the electrical integrity of the existing system. In addition, there are physical problems in retrofitting a system that is complex and very compact.
Another problem is that the monitoring function cannot always be performed by a human operator especially where the number of components to be monitored is great, or if the location to be monitored is remote. It can often happen, therefore, that a malfunction can go undetected for a prolonged period, perhaps leading to a chain of failures of far greater significance than the original. In addition, remote trouble-shooting and corrective measures that are now available are of reduced utility unless means are provided for quickly identifying the need for such measures. The present invention supplies this need in a most efficient and flexible manner, i.e., in a manner that is readily adaptable to a wide range of preexisting systems.